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The polymorphism of 23 microsatellites in the four main cattle breeds in Belgium (Holstein Friesian, Belgian Blue, Belgian Red Pied and East Flemish) was analysed. Heterozygosity, polymorphism information content, the effective number of alleles, exclusion probability and the probability of genotypic identity for two random individuals were calculated for all microsatellites and all breeds. The Belgian Blue breed is generally a little less polymorphic in comparison with the other three breeds. Estimates of the genetic distances between these breeds confirmed the widely accepted proposition that the Belgian Blue is the most genetically distinct of these breeds. The three other breeds are likely to become one population, given current breeding strategies. Exclusion probabilities in parentage control cases are > 0.9999 in all four breeds when all 23 microsatellites are used and > 0.98 with only the two most polymorphic multiplexes.

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Summary Genetic variability within four Belgian pig breeds, (Landrace (BL), Negative (BN), Piétrain (P), and Large White (LW)) was investigated using seven microsatellite loci. Differences in allele frequencies indicate each breed's particular identity. Computation of polymorphism information contents (PIC), theoretical heterozygosities, effective numbers of alleles, and probabilities of encountering, at random, two identical individuals in each breed revealed a variability, decreasing in the order LW, BN, BL, and P. Five types of genetic distance between the breeds were also calculated. Two‐by‐two breed comparisons indicated some distances to be rather important, confirming the breeds' morphological differences. BL and BN show the closest resemblance, while P is the most distant breed. The chances of encountering, at random, two identical individuals among two breeds are small, and confirm the conclusions resulting from the genetic distances. The efficiency of the microsatellites in parentage control is high. Zusammenfassung 7 Microsatellitsystemen studiert in 4 Belgische Schweinerassen Anhand von 7 Microsatellitsystemen wurde die genetische Variabilität innerhalb 4 Belgischer Schweinerassen (Landrasse [BL], Negativ [BN], Pietrain [P] und Large White [LW] untersucht. Unterschiede in Allelhäufigkeiten deuten auf die besondere Identität jeder einzelnen Rasse. Berechnung von Polymorphismus, Informationsinhalt (PIC), theoretischer Heterozygotiewerte, wirksamer Anzahl von Allelen und Wahrscheinlichkeit zweier identischer Individuen in jeder Rasse brachte Hinweise auf abnehmende Variabilität in der Reihenfolge von LW, BN, BL und P. Ausserdem wurden 5 Arten genetischer Distanzen zwischen den vier Schweinerassen berechnet. Bei paarweisem Vergleich zeigten diese Distanzen sich als ziemlich gross, so dass damit die morphologischen Differenzen zwischen den Rassen bestätigt werden. BL und BN haben die engste Verwandtschaft und P ist am weitesten entfernt von BL, BN und LW. Die Wahrscheinlichkeit, zufällig zwei identische Tiere in zwei Rassen zu finden, fehlt praktisch und bestätigt die Schlussfolgerungen, die sich aus den genetischen Distanzen ergeben. Die Microsatelliten sind sehr zweckmässig anwendbar in der Abstammungskontrolle.

A detailed physical map of the porcine MHC class III region on Chr 7 was constructed with a panel of probes in a series of hybridizations on genomic pulsed field gel electrophoresis (PFGE) Southern blots. A precise organization of the 700-kb segment of DNA between G18 and BAT1 can now be proposed, with more than 30 genes mapped to it. Comparison of this region with homologous regions in human and mouse showed only minor differences. The biggest difference was observed in the CYP21/C4 locus with only one CYP21 gene and one C4 gene found, whereas in human and mouse these genes are duplicated. These results show the class III region is very well conserved between pig, human, and mouse, in contrast with the class I and class II regions, which seem more prone to rearrangements.